WASHINGTON — President Trump said Friday he was surprised by allegations of domestic violence against his staff secretary that forced the top aide to resign this week — but lauded the work Rob Porter did and noted that that he has maintained his innocence.

"We found out about it recently and I was surprised by it, but we certainly wish him well and it's a tough time for him," Trump said. "He did a very good job when he was in the White House."

Trump's comments Friday were the first time the president has spoken publicly about the top aide since the allegations surfaced Wednesday in a report in the British tabloid The Daily Mail.

Trump said he was saddened by the allegations but said Porter has denied the accusations.

"He also, as you probably know, says he's innocent and I think you have to remember that," Trump told reporters in the Oval Office in an unscheduled photo-op. "He said very strongly yesterday that he's innocent so you have to talk to him about that, but we absolutely wish him well, he did a very good job when he was at the White House."

Those pleas of innocence come despite public accusations by two ex-wives — one of whom produced photos of a black eye she said Porter gave her while in Italy. In a written statement sent through the White House press office Wednesday, Porter said he took those photos, but that "the reality behind them is nowhere close to what is being described," he said. He did not elaborate.

The staff secretary is one of a small circle of top aides to the president, controlling the information flow into and out of the Oval Office — including some of the most classified and sensitive documents the president sees. Like many White House jobs, the position requires a security clearance.

The episode has raised questions about who in the White House knew of the issue, and whether presidential aides have been properly vetted. Both ex-wives have said they told FBI agents of the incidents during their background check investigation, but Porter was allowed to remain on the job with a temporary clearance for more than a year.

Democratic senators wrote Friday to White House Chief of Staff John Kelly and Counsel Don McGahn, demanding answers.

"We recognize that you and the president have tremendous discretion in deciding whom to hire to work in the White House," they wrote. "However, we are troubled by published accounts suggesting that you decided to hire Mr. Porter despite the fact he could not get a security clearance and that you were aware of the specific domestic violence allegations made against him."

For his part, Trump avoided those questions on Friday.

"We hope he has a wonderful career and he will have a great career ahead of him," Trump said of the 40-year-old aide. "He did a very good job when he was at the White House."

In an interview with NBC News in Pyeongchang, South Korea, Vice President Pence said he was "appalled" by the allegations and promised to personally look into them when he returns to Washington from the Winter Olympics.

"There's no tolerance in this White House, and no place in America for domestic abuse," Pence said.

President Trump speaks to reporters in the Oval Office of the White House, Friday.(Photo: Evan Vucci, AP)